This i a national stage application of JP97/00623 filed Feb. 28, 1997.
The present invention relates to a glass material for carrying a photocatalyst, a filter device using the same and a light irradiating method, particularly for improving an efficiency of light irradiation to a photocatalyst and increasing a photocatalyst reaction.
A photocatalyst reaction is characterized in oxidization reaction using a string oxidizing force produced under light irradiation. Therefore, attempts are positively made to utilize this technique in a filter and applies the technique to water treatment and environmental purifying.
As a filter using a conventional photocatalyst, a filter with TiO2 or another photocatalyst carried on a thermal resistant fiber or a porous substance, a filter with TiO2 or another photocatalyst carried on a metallic mesh, or the like is used. With a light from a luminous source, photocatalyst action is attained.
As specific examples available are a filter provided with a honeycomb cell carrying a photocatalyst inside a reaction container containing a reaction solution and a reaction solvent and an optical fiber for guiding light in the cell (Document 1. Publication of the patent application laid-open No. Hei 5-154387); a filter with a translucent thin film of titanium oxide carried on a flat substrate of a glass, ceramic or another style or on glass beads or ceramic halls for removing toxic substance contained in city water or the like by irradiating a light to the thin film (Document 2. Hashimoto and Fujishima, xe2x80x9cWater and Drainxe2x80x9d Vol.36 No.10 (1994), p5-11); a filter with photocatalysts carrying titanium oxide powder on a honeycomb carrier positioned at both sides of a luminous source for purifying air inside an automobile or various environments (Document 3. Suzuki, xe2x80x9cToyotta Chuo Kenyasho RandD Reviewxe2x80x9d Vol.28 No.3 (1993.9), p47-56); a filter with a TiO2 pellet positioned inside an annular container having a luminous source in its middle for treating trichloroethylene or another volatile organic chlorine compound (Document 4. Yamazaki, xe2x80x9cChemistry and Industryxe2x80x9d, Vol.47 No.2 (1994) p152-155); and the like.
However, in either of the aforementioned prior arts, a photocatalyst action is produced with a light from a luminous source slightly apart from a photocatalyst. Therefore, following common problems exist.
(1) If a filter is covered with dirt, dust, sludge or the like, light has difficulty in reaching a photocatalyst, thereby decreasing a catalyst function. For this, very strong ultraviolet rays are necessary. Especially in case of almost black sewage raw water containing a large quantity of substances, light does not reach a photocatalyst, and a photocatalyst reaction is inactivated or only slightly activated, which cot be practically used.
(2) Light strikes portions and does not strike other portions, and only the light struck portions act. To eliminate the disadvantage, a hybrid photocatalyst is prepared by mixing adsorbent and titanium oxide. The portions not struck by light are collected with the adsorbent and moved to the light-struck portions for decomposition. Such a complicated system needs to be designed.
(3) Even when light irradiates a photocatalyst from a luminous source to a photocatalyst, only a slight quantity of the irradiated light can reach the photocatalyst. Most of the light energy is wasted. Therefore, to efficiently irradiate light, the designing of a device is Important. For this, a structure provided with an annular container having inside a photocatalyst and a luminous source in its middle or another complicated structure needs to be designed.
An object of the invention is to provide a photocatalyst filter, its device and a fluid treatment method using the same which can solve the aforementioned prior-art problem and efficiently produce a photocatalyst function by a sample structure of irradiating light f m a support body carrying a photocatalyst directly to the photocatalyst.
Also, to enhance a capacity for treatment such a photocatalyst, a large quantity of light is heretofore introduced to the photocatalyst.
Specifically, the conventional application of the photocatalyst are restricted to the following.
(1) To enhance the capacity, the irradiation of a large quantity of light is devised.
(2) To enhance the capacity, a way of light irradiation is devised.
(3) To enhance the capacity, the increasing of a photocatalyst activity is devised.
(4) The low capacity restricts the application to the commercial goods developed in accordance with the capacity: for example, deodorization (treating a small quantity, with a rate-determining step in diffusion); prevention of pollution (treating a all quantity over a long time period); antibacterial treatment (treating a small quantity: sterilization is impossible) and the like.
In this manner, even when a photocatalyst action is used, the development giving weight to a light quantity restricts enhancement in capacity of a photocatalyst reaction. When there are a large quantity of objects of photolysis, they cannot be treated by the action of a photocatalyst.
The present invention has been developed in the aforementioned background, to provide a photocatalyst filter device and a filtering method which can remarkably enhance a filtering capacity.
Here, as a filter used for filtering gas, liquid or another fluid generally known is a filter having a filtering face vertical to a passage of fluid to be filtered (e.g. the patent application laid-open No. Hei 7-224632); a filter having a filtering face parallel with a passage of fluid (e.g. the patent application laid-open No. 56-129020) or the like.
In the former, to increase a filtering capacity, a filtering area orthogonal to the passage needs to be enlarged. However, if the passage is enlarged in the vicinity of the filter, it is difficult to uniformly hold the fluid pressure exerted to each portion of the filter. Therefore, the collecting density disadvantageously not uniform, and an efficient filtering cannot be attained.
For the latter, since the filtering face is parallel with the passage, it is effective in that the passage does not have to be necessarily enlarged because the latter has a larger filtering area as compared with the former. However, then the fluid to be filtered advances in a filtering portion, the fluid to be filtered is gradually discharged to the outside through the filtering face serving also as the passage. Therefore, there arises a difference in pressure among respective filter portions, which cases a deviation in collecting density. Therefore, a sufficiently efficient filtering cannot be attained.
Also, attempts are being made to apply a photocatalyst reaction to various water treatment, air treatment, and environmental purifying. However, even if the reaction is used in the aforementioned filter, it is very difficult to irradiate light all over the filter.
The invention has been developed in the aforementioned background, and its object is to provide a filter device which can obtain an efficient filtering action and can be effectively given a filter purifying function using a photocatalyst reaction.
When fluid is to be filtered by a filter, generally following three types of filters are used.
The first type is a filter using a short-fibrous fiber (hereinafter referred to as the short-fibrous filter).
The second type is a filter using a long-fibrous fiber (hereafter referred to as the long-fibrous filter). A base material of the filter is in a form of cloth woven with a long-fibrous fiber.
The third type is a filter using particulates (including a porous body), or a porous body formed by sintering the particulates. Alternatively, the filter is formed by filling a filter forming space with the particulates.
However, either of the aforementioned conventional type filters has the following problems. It is difficult to provide a sophisticated filter inexpensively.
First, in the first type of short-fibrous filter, a fiber filling density is changed mainly by adjusting filter holes (mesh). A localized difference in density is easily made. It is difficult to precisely control the mesh. When fluid is passed, the configuration of the mesh is changed, or another problem arises. Therefore, problem is that it is difficult to obtain a sophisticated filter.
In the second type of long-fibrous filter, an intricate process for Raving a long-fibrous fiber into a cloth is necessary, which increases cost. Additionally, a weavable fiber diameter has its limitation. Attainable mesh is restricted. Therefore, there is also a problem that it is difficult to obtain a sophisticated filter.
Further in the third type of filter using particulates (including a porous body), the filter is formed by filling a filter forming space with the particulates. To obtain a filter function, a considerable quantity of particulates are necessary. This raises a problem that a large space is necessary and cost is increase.
Also in the third type of filter, particulates are formed by sintering or another process into a porous filter for use. A considerably quantity of particulates are necessary. This also raises the aforementioned problem that a large space is necessary and cost is increased. Additionally, there arises a problem that the cost required for forming further increases cost.
The invention has been developed by considering the aforementioned problems, and its object is to prove a filter material, its manufacture method and a filter device or the like using the filter material, so that a sophisticated filter can be provided inexpensively.
As a carrier of the aforementioned photocatalyst filter or another photocatalyst, various glasses are used.
However, it is reported that soda lime glass base material is not preferable because of its deteriorated photocatalyst activity. This is probably because sodium ions are diffused in the photocatalyst to form compounds when the photocatalyst is thermally oxidized.
On the other hand, quartz glass has no diffusion of impurities in a photocatalyst and is surely preferable as a photocatalyst carrying base material. H its manufacture cost is high for practical use. Also, glass has such a high softening temperature that it is difficult to be hot-,worked into various configurations. Cost is further increased.
Further, attempts are made of coating a surface of soda lime glass with quartz glass to suppress sodium from eluting. However, a thin film cannot provide a sufficient effect, while cost is required for forming the thin film, which is undesirable.
The invention has been developed by considering the aforementioned circumstances, and its object is to provide a photocatalyst carrying glass material which has no diffusion of impurities in a photocatalyst, therefore, has its photocatalyst activity not deteriorated, further can be provided inexpensively.
In addition to the aforementioned photocatalyst filter, in case of photo reaction and thermal reaction using light or other cases, light needs to efficiently irradiate a matter to be irradiated. However, according to the invention, a light irradiating method and its device can be applied particularly when light irradiates a photochemical reaction system, or thermal energy is transmitted to a chemical reaction system.
When light irradiates the photochemical system, in most cases, light is irradiated from a single direction. Also, photo-reaction starts from photo-absorption on a surface of a reactant.
In case of thermal reaction, heating is performed directly with a heater or atmospheric heating is performed. In either heating method, thermal reaction starts from a surface close to a thermal source.
In case of combustion reaction, source fire is used, or atmospheric heating is performed. Also in this case, combustion reaction starts from a portion of a reactant close to source fire. In the atmospheric heating, the reaction starts from a surface of the reactant.
In case of conventional photo-reaction, since an exposed surface of a reactant is limited, a tire lag is caused in starting reaction between a portion near the surface and a portion far from the surface. Also, since the exposed surface of the reactant is limited, reaction advances only in a surface portion. Further, when the reactant has a high t n, light has difficulty in reaching the reactant, therefore an intense light needs to be irradiated. Also, w either side of the reactant has a solid phase, to irradiate much light to the solid phase, a luminous source is arranged in multiple directions or the structure needs to be complicated otherwise.
On the other hand, in case of conventional thermal reaction (combustion reaction), in the same manner as in photo-reaction, since an exposed surface of a reactant is limited, a time lag is caused in starting reaction between a portion near the surface and a portion far from the surface. Also, since the exposed surface of the reactant is limited, reaction advances only in a surface portion. Also, to enhance the heat conduction efficiency, sufficient stirring is always necessary. When there arises a temperature gradient in the reactant, a partial difference in reaction is caused. Further in the conventional thermal reaction, since heating is performed using heat conduction and convention, it is difficult to control a constant temperature. It is also difficult to prepare many surfaces.
The invention has been developed to solve the aforementioned problems, and its object is to provide a light irradiating method and its device which basically supplies light and heat through a light guiding body, and promotes photochemical reaction and efficiently transmits heat energy by means of a structure with the light guiding body itself as an irradiator
The objects of the invention are achieved by constitutions of the invention recited in claims. The invention recited in each claim is closely interrelated.
According to the present invention a novel photocatalyst filter is provided by forming a photocatalyst layer on the surface of a light guiding filter body, preferably a glass fiber support, to receive light for the activation of the photocatalyst.
Further a light irradiating method is provided by said filter device.
The photocatalyst filter according to the invention is constituted in such a manner that a photocatalyst is carried on a surface of a light guiding body for guiding light needed to activate the photocatalyst, and the light guided by the light guiding body irradiates directly from a surface of the light guiding body the photocatalyst.
When the light necessary for activation irradiates the photocatalyst, the photocatalyst causes a photalyst reaction, produces a strong oxidizing force and a reducing force on its surface and fulfills a capacity of decomposing and removing a substance contacting the photocatalyst.
As said light guiding body, at least one material selected from the group consisting of glass, ceramic, plastic and crystal which does not react with the photocatalyst itself can be used.
Said light guiding body can be formed in either one or two or mire configurations of a fiber, a honeycomb, a mesh, a cloth, a layer and a cotton.
The photocatalyst is preferably transparent relative to the light necessary for its activation, or can be opaque. In case of an opaque photocatalyst, a large number of photocatalysts are carried like islands on the surface of the light guiding body, so that the light emitted from the portion carrying no photocatalysts of the surface of the light guiding body surrounds peripheries of the opaque photocatalysts.
As said photocatalyst, one or two or more can be used from titanium oxide, iron oxide or its compound, zinc oxide or, ruthenium oxide or its compound, cerium oxide, tungsten oxide or its compound, molybdenum oxide, cadmium oxide or its compound, and strontium oxide or compounds which generate any of these oxides.
The photocatalyst layer may be applied by means of a sol-gel method, a peraeosol method, a wash/coat method, an evaporation method, a sputtering method, a thermal decomposition method, a metal oxidizing nod or the like. By using one or two or more of these method, the surface of the light guiding body is covered with a 1 nm to 1 mm thick film.
Also, to the photocatalyst, an additive for reinforcing a photocatalyst active layer, reinforcing an a strength, reinforcing a stability, reinforcing a photo-reaction or providing another action can be added or used as an undercoat. As a substance, Cr, Ag, Cu, Au, Pt, Ru, Pd, Rh, Sn, Si, In, Pb, As, Sb, P or another metal, its oxide or its compound can be used. To enhance the adherence strength, instead of adding the additive, as a substrate layer of a catalyst layer, Cr, In, Sn, Si, P or the like can be provided.
Materials of the photocatalyst and the light guiding body are selected by considering a refractive index. Different from an optical fiber enclosing light in a core, light needs to be emitted at the side of the photocatalyst as a covering material. As compared with the material of the light guiding body, a photocatalyst having a larger refractive index may be selected.
Further, the photocatalyst filter according to the invention can be structured in such a manner that partially or wholly on an optical fiber having a clad provided on an outer periphery of a core constituting said light guiding body, a core exposed portion lacking said clad is formed, and on the core exposed portion, a photocatalyst having a higher refractive index than the core is carried.
The pbotocatalyst filter of said constitution and a luminous source for injecting light to said photo guiding body can be combined to form a photocatalyst filter device.
For a luminous source, when the photocatalyst is TiO2, its wavelength is preferably in an ultraviolet range of 200 nm to 500 nm which can activate the photocatalyst. A mercury lamp or an ultraviolet lamp for outputting a continuous light can he used. Light from the luminous source may be injected to the light guiding body in one direction or two or more directions.
The photocatalyst filter device according to the invention is a photocatalyst filter device for removing particles matter captured by a filter constituted of a filter material carrying a photocatalyst by using a photolysis reaction of said photocatalyst, and is provided with a heating means for heating said captured matter and/or said photocatalyst.
By combining this filter device with a luminous source for supplying light to a photocatalyst carried on said filter material, a fluid to be filtered is filtered with a filter of said photocatalyst filter device, and light irradiates from said luminous source said photocatalyst for photolysis of the matter captured by said filter, he by heating said captured matter and/or said photocatalyst with said heating means, carbon included in the captured matter is oxidized and gasified, so that the captured matter can be removed.
Said filter material can be constituted of one or two or more selected from the group consisting of glass, ceramic, crystal, metal and plastic. A heating temperature with said heating means is usually selected from 50 to 650xc2x0 C. For glass as the filter material, the selected temperature is a glass transition point or less: for ceramic, a decomposition point or less; for plastic, the lower temperature of a melting point and a decomposition point of its crystal or less; and for metal, a melting point or less, respectively.
Said filter material can be formed in a structural body of one or two or more configurations selected from the group consisting of a fiber, a honeycomb, a mesh, a cloth, a layer, a cotton and a particulate.
Also, the filter device according to the invention is a filter device using as a filter material an aggregate formed by bundling a large number of long-fibrous bodies aligned in a longitudinal direction, an elongate structural body is formed of said filter material and has one end the open and the other end closed the opening with having its size gradually reduced in longitudinal direction toward the other end, and the matter to be filtered flows through the elongate body via said opening.
Said long-fibrous body partially or wholly forms a wave form in the longitudinal direction.
Also, on a surface of said long-fibrous body, protrusions can be formed.
Said long-fibrous body is partially or wholly constituted of a light guiding material, and may have a photocatalyst partially or wholly formed on its surface.
Further, by introducing light from one end of said long-fibrous fibrous into said long-fibrous body and supplying light to the photocatalyst formed on the surface of said long-fibrous body, a photocatalyst action is produced, so that matters sticking to the surface of said long-fibrous body can be decomposed/removed.
The filter device can be constituted of one or two types or more of an extra fine glass fiber with a diameter of 1 to 70 microns.
Said extra fine glass fiber can be constituted as a structural body of one or two or more configurations selected from the groups consisting of a bundle, a mesh, a cloth, a layer and a candle.
Further in said filter device, a softening point of said extra fine glass fiber is preferably 700xc2x0 C. or more.
Further in said filter device, partially or wholly on a surface of said extra fine glass fiber, a photocatalyst is formed.
Further in said filter device, by introducing light from one end of said extra fine glass fiber into said extra fine glass fiber and supplying light to the photocatalyst formed on the surface of said extra fine glass fiber, a photocatalyst action is produced, so that matters sticking to said extra fine glass fiber can be decomposed/removed.
In said filter device, a first heating means is provided for heating said captured matter.
The filter material of the filter according to the invention has a constitution with protrusions formed on the surface of the filter base material.
A manufacture method of the filter material according to the invention is constituted in such a manner that protrusions are formed on the surface of the filter base material.
For a manufacture method of a filter material of the invention, said manufacture method of the filter material of the invention has:
a constitution of forming protrusions by fixing particulates on a surface of a filter base material;
a constitution of forming protrusions by using a metallic mold on the surface of the filter base material; or
a constitution of forming protrusions on the surface of the filter material by mixing materials in a filter raw base material and shaping.
The filter device of the invention is constituted by using a filter material with protrusions formed on its surface.
A pitch of said protrusion is 2d to 20d, preferably 3d to 10d relative to a diameter d of a long-fibrous body, and a diameter of the protrusion is selected from the range of 0.3 to 100 xcexcm.
Further, the filter device of the invention is constituted by using the filter material with protrusions formed on its surface and said filter material partially or wholly carrying a substance for promoting a catalyst or a surface reaction, or constituted by using the filter material having a light guiding property with protrusions formed on its surface, said filter material partially or wholly carrying a photocatalyst, so that the light irradiated to the filter material and guided via the inside of the filter material irradiates the photocatalyst.
According to the invention, by changing a size of protrusions or a distribution density of protrusions, vacancy (mesh) can be easily controlled with high accuracy. Also, a filter can be obtained only by bundling or laminating the filter material with protrusions formed thereon. Therefore, a not-conventional sophisticated filter can be obtained inexpensively.
Also, since holes or gaps are obtained by the protrusions formed on the surface of the filter material, the holes or gaps remain unchanged even when fluid is passed, and vacancy can be maintained over a long time period. Therefore, the performance as a filter can be maintained over a long time period.
Further, in the invention, a weaving process is basically unnecessary. Even a long-fibrous fiber with a fiber diameter heretofore difficult to be used as a long-fibrous filter can be used as a filter material.
Also, since protrusions are formed on the surface of the filter material, as compared with the filter material having no protrusions, an efficiency can be enhanced in a filter having a function of purifying fluid by using a surface reaction.
A photocatalyst carrying glass material used as the filter or the light guiding body of the filter device according to the invention contains 30 to 80% of SiO2 and 0 to 10% of alkali component in terms of weight %, and is constituted of a low-alkali silicate glass, an alumino-silicate glass, a borosilicate glass or a non-alkali glass.
Also, the photocatalyst carrying glass material of the invention contains, in terms of weight %, 30 to 80% of SiO2, 1 to 35% of Al2O3, 0 to 30% of B2O3, 0 to 20% of MgO, 0 to 20% of CaO, 0 to 20% of SrO, 0 to 40% of BaO, 0 to 20% of ZnO, 0 to 10% of Li2O, 0 to 10% of Na2O, 0 to 10% of K2O, 0 to 10% of Cs2O, 0 to 10% combined content of Li2O+Na2O+K2O+Cs2O and 0.1 to 65% combined content of MgO+CaO+SrO+BaO+ZnO+Li2O+Na2O+K2O+Cs2O.
Further, the photocatalyst carrying glass material of the invention contains, in terms of weight %, 30 to 60% of SiO2, 1 to 20% of Al2O3, 0 to 20% of B2O3, 0 to 20% of MgO, 0 to 20% of CaO, 0 to 20% of SrO, 0 to 40% of BaO, 0 to 20% of ZnO, 1 to 60% combined content of MgO+CaO+SrO+BaO+ZnO, 0 to 10% of Li2O, 0 to 5% of Na2O, 0 to 5% of K2O, 0 to 5% of Cs2O, 0 to 5% of combined content Li2O+Na2O+K2O+Cs2O and 1 to 60% combined content of MgO+Cao+SrO+BaO+ZnO+Li2O+Na2O+K2O+C2O.
For the photocatalyst carrying glass material of the invention, said photocatalyst carrying glass material contains as other components at least one component selected from the group consisting of PbO, ZrO, Tio2, As2O3, Sb2O3, SnO2, La2O3, P2O5, WO3, Bi2O3, Ta2O5, Nb2O5, Gd2O3 and F.
Alternatively, a transmittivity in a wavelength for activating a photocatalyst is 75% or more at a thickness of 10 mm.
The invention uses the glass composition having no diffusion of impurities in the photocatalyst, having photocatalyst activity not deteriorated, having a photocatalyst thin film easily formed thereon, being superior in chemical durability, transparency and the like, and able to be manufactured inexpensively, and is, therefore, superior as the photocatalyst carrying glass material.
Further by adjusting the position, a fine fiber can be easily obtained, and a photocatalyst carrying glass material superior in heat resistance and other properties can be obtained inexpensively.
First as the aforementioned photocatalyst filter, and as a light irradiating method applicable when light needs to efficiently irradiate an object to be irradiated, the invention provides a light irradiating method in which a highly refractive substance having a higher refractive index than a light guiding body is carried on a surface of said light guiding body, and light guided by the photo guiding body and leaking from said highly refractive substance irradiates the object to be irradiated.
Said light guiding body is constituted of at least one material selected from glass, ceramic, plastic and crystal.
Said light guiding body is formed in either one or two or more configurations of a fiber, a honeycomb, a mesh, a cloth, a layer and a cotton.
Also in the light irradiating method according to the invention, partially or wholly on an optical fiber having a clad provided on an outer periphery of a core, a core exposed portion lacking said clad is formed, and on the core exposed portion, said highly refractive substance is carried, so that the light guided in the core and leaking from said highly refractive substance irradiates to the object to be irradiated.
Said highly refractive substance is constituted of at least one or more materials selected from glass, ceramic, plastic and crystal.
Also in a light irradiating device according to the invention, on a surface of a light guiding body, a highly refractive substance having a higher refractive index than said light guiding body is carried, and the light guided by the light guiding body and leaking from said highly refractive substance irradiates the object to be irradiated.
Further in a filter device according to the invention, on a surface of a light guiding body, a highly refractive substance having a higher refractive index than said light guiding body is carried.
The light guided by the light guiding body leaks from said highly refractive substance, and the leaking light burns collected matters.
Further in a ultraviolet sterilizing device according to the invention, on a surface of a light guiding body, a highly refractive substance having a higher refractive index than said light guiding body is carried.
The ultraviolet ray guided by the light guiding body leaks from said highly refractive substance, and the leaking ultraviolet light sterilizes matters to be sterilized.
Then, in the aforementioned respective inventions, when light necessary for each reaction is irradiated, a reaction system, in response to the light, produces a photo-reaction, a thermal reaction, a combustion reaction or the like. As a luminous source wavelength, a visible ultraviolet ray can be used in the photo reaction, an infrared ray can be mainly used in the thermal reaction and an intense visible infrared ray can be mainly used in the combustion reaction. Light from the luminous source may be injected to the light guiding body in one direction or two or more directions.
As a carrying method of a highly refractive substance used is a sol-gel method, a peraerosol method, a wash/coat method, an evaporation method, a sputtering method, a thermal decomposition method, a metal oxidizing method, a double crucible method, a rod in tube method or the like. By using one or two or more of these methods, the surface of the light guiding body is covered with a 1 nm to 1 mm thick film.
Also, to the highly refractive substance, an additive for providing light selection, reinforcing an adherence strength, reinforcing a stability, reinforcing a photo-reaction or providing another action can be added or used as an undercoat. As a substance, Cr, Ag, Cu, Au, Pt, Ru, Pd, Rh, Sn, Si, In, Pb, As, Sb, P or another metal, its oxide or its compound can be used. To enhance the adherence strength, instead of adding the additive, as a substrate layer of a highly refractive substance layer, Cr, In, Sn, Si, P or another metal, its oxide or its compound can be provided.